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Articles 1 - 9 of 9

Full-Text Articles in Physics

Growth And Characterization Of Baznga, Na Hyun Jo, Qisheng Lin, Udhara S. Kaluarachchi, William R. Meier, Soham Manni, Savannah S. Downing, Anna E. Böhmer, Tai Kong, Yang Sun, Valentin Taufour, Cai-Zhuang Wang, Kai-Ming Ho, Sergey L. Bud’Ko, Paul C. Canfield Jan 2017

Growth And Characterization Of Baznga, Na Hyun Jo, Qisheng Lin, Udhara S. Kaluarachchi, William R. Meier, Soham Manni, Savannah S. Downing, Anna E. Böhmer, Tai Kong, Yang Sun, Valentin Taufour, Cai-Zhuang Wang, Kai-Ming Ho, Sergey L. Bud’Ko, Paul C. Canfield

Ames Laboratory Accepted Manuscripts

We report the growth, structure and characterization of BaZnGa, identifying it as the sole known ternary compound in the Ba–Zn–Ga system. Single crystals of BaZnGa can be grown out of excess Ba–Zn and adopt a tI36 structure type. There are three unique Ba sites and three M = Zn/Ga sites. Using DFT calculations we can argue that whereas one of these three M sites is probably solely occupied by Ga, the other two M sites, most likely, have mixed Zn/Ga occupancy. Temperature-dependent resistivity and magnetization measurements suggest that BaZnGa is a poor metal with no electronic ...


Flux Requirements For The Growth Of Rfeaso (R = Rare Earth) Superconductors, J.-Q. Yan, Brandt A. Jensen, Kevin W. Dennis, R. William Mccallum, Thomas A. Lograsso Feb 2011

Flux Requirements For The Growth Of Rfeaso (R = Rare Earth) Superconductors, J.-Q. Yan, Brandt A. Jensen, Kevin W. Dennis, R. William Mccallum, Thomas A. Lograsso

Ames Laboratory Publications

Millimeter-sized LaFeAsO single crystals have been successfully grown out of NaAs flux starting with (LaAs+1/2Fe2O3):20NaAs. The factors which allow the growth of these crystals out of NaAs but not out of many other fluxes, such as FeAs, have been investigated. X-ray powder diffraction found that NaAs synthesized for the growth ofRFeAsO superconductors has monoclinic LiAs structure. Thermal analysis confirmed that NaAs melts congruently at about 600 °C. The ability to extract RFeAsO crystals from this NaAs flux suggests that NaAs has a significant oxygen solubility, possibly due to the formation of ...


Layer-By-Layer Photonic Crystal Fabricated By Low-Temperature Atomic Layer Deposition, Jae-Hwang Lee, Wai Y. Leung, Jinho Ahn, Tasho Lee, In-Sung Park, Kristen P. Constant, Kai-Ming Ho Jan 2007

Layer-By-Layer Photonic Crystal Fabricated By Low-Temperature Atomic Layer Deposition, Jae-Hwang Lee, Wai Y. Leung, Jinho Ahn, Tasho Lee, In-Sung Park, Kristen P. Constant, Kai-Ming Ho

Materials Science and Engineering Publications

Layer-by-layer three-dimensional photonic crystals are fabricated by low-temperature atomic layer deposition of titanium dioxide on a polymer template created by soft lithography. With a highly conformal layer of titanium dioxide, a significantly enhanced photonic band gap effect appears at 3.1μm in transmittance and reflectance. From optical investigations of systematically shifted structures, the robust nature of the photonic band gap with respect to structural fluctuations is confirmed experimentally. With angle-resolved Fourier-transform spectroscopy, the authors also demonstrate that the fabricatedphotonic crystal can be a diffraction-free device as the photonic band gap exists over the diffracting regime.


Variation Of Magnetostriction With Temperature In Tb5si2.2ge1.8 Single Crystal, A. P. Ring, H. L. Ziegler, Thomas A. Lograsso, Deborah L. Schlagel, J. E. Snyder, David C. Jiles Apr 2006

Variation Of Magnetostriction With Temperature In Tb5si2.2ge1.8 Single Crystal, A. P. Ring, H. L. Ziegler, Thomas A. Lograsso, Deborah L. Schlagel, J. E. Snyder, David C. Jiles

Ames Laboratory Conference Papers, Posters, and Presentations

The Tb5(SixGe4−x) alloy system is similar to the better known Gd5(SixGe4−x), except it has a more complex magnetic and structural phase diagram. Gd5(SixGe1−x)4 has received much attention recently due to its giant magnetocaloric effect, colossal magnetostriction and giant magnetoresistance in the vicinity of a first order combined magnetic-structural phase transition. The magnetostriction changes that accompany the phase transitions of single crystal Tb5(Si2.2Ge1.8) have been investigated at temperatures between 20 and150 K by measurements of ...


Three-Dimensional Metallic Photonic Crystals Fabricated By Soft Lithography For Midinfrared Applications, Jae-Hwang Lee, Chang-Hwan Kim, Yong-Sung Kim, Kai-Ming Ho, Kristen P. Constant, Cha-Hwan Oh Jan 2006

Three-Dimensional Metallic Photonic Crystals Fabricated By Soft Lithography For Midinfrared Applications, Jae-Hwang Lee, Chang-Hwan Kim, Yong-Sung Kim, Kai-Ming Ho, Kristen P. Constant, Cha-Hwan Oh

Materials Science and Engineering Publications

We present an efficient method of fabricating freestanding three-dimensional metallic photonic crystals using soft lithography. Low cost and ease of fabrication are achieved through gold sputter deposition on a freestanding woodpile polymer template. We compare experimental results to theoretical calculations for tetragonal and face-centered-tetragonal structures as a function of the number of layers. The photonic crystals behave like full metallic structures with a photonic band edge at a wavelength of 3.5μm. The rejection rates of the structures are about 10dB/layer.


Reflectance Anisotropy Of Gd5si2ge2 And Tb5si2.2ge1.8, S. J. Lee, Joong Mok Park, J. E. Snyder, David C. Jiles, Deborah L. Schlagel, Thomas A. Lograsso, A. O. Pecharsky, David W. Lynch Mar 2004

Reflectance Anisotropy Of Gd5si2ge2 And Tb5si2.2ge1.8, S. J. Lee, Joong Mok Park, J. E. Snyder, David C. Jiles, Deborah L. Schlagel, Thomas A. Lograsso, A. O. Pecharsky, David W. Lynch

Ames Laboratory Publications

Reflectance difference (RD) spectra for the ab plane of the single crystals of Gd5Si2Ge2and bc planes of Gd5Si2Ge2 and Tb5Si2.2Ge1.8 were obtained in the photon energy range of 1.5–5.5 eV. Several peaks were observed for these crystals in the measured spectrum range. Similar features were observed in the RD spectra for the bc planes ofGd5Si2Ge2 and Tb5Si2.2Ge1.8, while different features were observed for the ...


Fabrication Of Photonic Band Gap Crystal Using Microtransfer Molded Templates, Wai Y. Leung, Henry Kang, Kristen P. Constant, D. Cann, Chang-Hwan Kim, Rana Biswas, M. M. Sigalas, Kai-Ming Ho Jan 2003

Fabrication Of Photonic Band Gap Crystal Using Microtransfer Molded Templates, Wai Y. Leung, Henry Kang, Kristen P. Constant, D. Cann, Chang-Hwan Kim, Rana Biswas, M. M. Sigalas, Kai-Ming Ho

Materials Science and Engineering Publications

We have proposed and demonstrated an economical technique to fabricate a three-dimensional layer-by-layer photonic band gapstructure in the infrared wavelengths. An organic polymer template structure, an inverse layer-by-layer photonic crystalstructure, is assembled using the microtransfer molding technique. This template is infiltrated with sol-gel or nanoparticle titanium oxide slurry, then later removed by heat treatment at a temperature range of 550–800 °C. This method can be extended to fabricatephotonic crystals operating at optical and ultraviolet frequencies.


Structural Studies Of Fe0.81ga0.19 By Reciprocal Space Mapping, D. Viehland, Jiefang Li, Thomas A. Lograsso, A. R. Ross, Manfred Wuttig Oct 2002

Structural Studies Of Fe0.81ga0.19 By Reciprocal Space Mapping, D. Viehland, Jiefang Li, Thomas A. Lograsso, A. R. Ross, Manfred Wuttig

Ames Laboratory Publications

Reciprocal lattice mapping has been performed on Fe0.81Ga0.19 crystals by ω–ω/2θ, Ψ–ϕ, and ω–ϕ scans. A strong elongation of the 〈001〉c peak was found along the〈110〉c direction. ω scans revealed short lateral correlation lengths ξ along 〈110〉cand strong diffuse scattering along the 〈001〉c. Multiple domains with monoclinic symmetry (angle ∼190°) were observed by Ψ–ϕ and ω–ϕ scans on the (001)c face, and were also tilted with respect to each other. The results show an average cubic structure with orthorhombic structural modulations, and ...


Magnetostriction Of Ternary Fe–Ga–X Alloys (X=Ni,Mo,Sn,Al), J. B. Restorff, M. Wun-Fogle, A. E. Clark, Thomas A. Lograsso, A. R. Ross, Deborah L. Schlagel May 2002

Magnetostriction Of Ternary Fe–Ga–X Alloys (X=Ni,Mo,Sn,Al), J. B. Restorff, M. Wun-Fogle, A. E. Clark, Thomas A. Lograsso, A. R. Ross, Deborah L. Schlagel

Ames Laboratory Publications

Investigations were made into the effect of small additions of Ni, Mo, Sn, as well as larger additions of Al on the magnetostriction of single crystal Fe100−xGax alloys (x≅13). The Fe–Ga and Fe–Al systems are seemingly unique among the Fe-based alloys in having very large magnetostrictions in spite of Ga and Al being nonmagnetic. In this paper, we show how additions of Ni, Mo, Sn, and Al affect λ100 and λ111 of the binary Fe–Ga alloys. We substituted small amounts of Ni into a binary Fe–Ga alloy in an ...